U.S. patent application number 17/110279 was filed with the patent office on 2021-03-25 for method of preparing cathode material for secondary battery.
The applicant listed for this patent is GRST International Limited. Invention is credited to Kam Piu Ho, Yingkai Jiang, Peihua Shen, Ranshi Wang.
Application Number | 20210091407 17/110279 |
Document ID | / |
Family ID | 1000005252016 |
Filed Date | 2021-03-25 |
United States Patent
Application |
20210091407 |
Kind Code |
A1 |
Ho; Kam Piu ; et
al. |
March 25, 2021 |
METHOD OF PREPARING CATHODE MATERIAL FOR SECONDARY BATTERY
Abstract
Provided herein is a method for preparing a ternary cathode
material for lithium-ion battery by a static mixer, wherein the
cathode material comprises a lithium multi-metal composite oxide
represented by
xLi.sub.2MnO.sub.3.(1-x)LiNi.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)O.sub.2-
, where 0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1, and 0.ltoreq.x<1. The cathode material disclosed
herein exhibits a high initial specific capacity, possesses good
safety characteristics and shows excellent capacity retention.
Inventors: |
Ho; Kam Piu; (Hong Kong,
HK) ; Wang; Ranshi; (Hong Kong, HK) ; Shen;
Peihua; (Guangzhou, CN) ; Jiang; Yingkai;
(Hong Kong, HK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GRST International Limited |
Hong Kong |
|
HK |
|
|
Family ID: |
1000005252016 |
Appl. No.: |
17/110279 |
Filed: |
December 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16313978 |
Dec 28, 2018 |
10903516 |
|
|
PCT/CN2017/115346 |
Dec 8, 2017 |
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17110279 |
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62435863 |
Dec 19, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/364 20130101;
H01M 10/0525 20130101; H01M 4/525 20130101; H01M 4/485 20130101;
H01M 4/505 20130101 |
International
Class: |
H01M 10/0525 20060101
H01M010/0525; H01M 4/36 20060101 H01M004/36; H01M 4/485 20060101
H01M004/485; H01M 4/505 20060101 H01M004/505; H01M 4/525 20060101
H01M004/525 |
Claims
1. A method of preparing a cathode material for a lithium-ion
battery cell, comprising the steps of: dissolving a combination of
at least three of a salt of nickel, a salt of manganese, a salt of
cobalt, and a salt of aluminium in water to obtain a first
solution, wherein a total molar concentration of the metal elements
in the first solution is from about 0.1 mol/L to about 3 mol/L;
dissolving a precipitating agent in water to form a second
solution, wherein a concentration of the precipitating agent in the
second solution is from about 0.5 mol/L to about 6 mol/L;
pre-heating the first solution and the second solution to the same
temperature from about 30.degree. C. to about 80.degree. C. to
obtain a pre-heated first solution and a pre-heated second solution
respectively; feeding the pre-heated first solution and the
pre-heated second solution to a first inlet and a second inlet of a
static mixer respectively to obtain a co-precipitating solution;
filtering a suspension eluted from an outlet of the static mixer to
obtain a cathode material precursor, wherein the outlet of the
static mixer is coupled to a pH controller for controlling the flow
rate of the pre-heated first and second solutions; washing the
cathode material precursor with water; drying the washed cathode
material precursor to obtain a dried cathode material precursor;
mixing the dried cathode material precursor with one or more
lithium salts to obtain a solid mixture, wherein a molar ratio of
the metal element lithium of the one or more lithium salts to the
total amount of the metal elements selected from a combination of
at least three of nickel, manganese, cobalt, and aluminium is from
about 1.5:1 to about 1:1, or from about 1.03:1 to about 1:1; and
calcining the solid mixture in two stages to obtain the cathode
material, wherein the first stage is conducted at a temperature
from about 350.degree. C. to about 550.degree. C. for a time period
from about 2 hours to about 10 hours, and the second stage is
conducted at a temperature from about 750.degree. C. to about
950.degree. C. for a time period from about 6 hours to about 15
hours, and wherein the cathode material comprises a lithium
multi-metal composite oxide represented by
xLi.sub.2MnO.sub.3.(1-x)LiNi.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)O.sub.2-
, wherein 0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1, and 0.ltoreq.x<1; and the cathode material has a
D90/D10 ratio from about 1.4 to about 1.9.
2. The method of claim 1, wherein the cathode material precursor is
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)](OH).sub.2 or
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)]CO.sub.3, wherein
0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1.
3. The method of claim 1, wherein the cathode material precursor is
selected from the group consisting of
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33](OH).sub.2,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2](OH).sub.2,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2](OH).sub.2,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2](OH).sub.2,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15](OH).sub.2,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1](OH).sub.2,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04](OH).sub.2,
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05](OH).sub.2,
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33]CO.sub.3,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2]CO.sub.3,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2]CO.sub.3,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2]CO.sub.3,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15]CO.sub.3,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1]CO.sub.3,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04]CO.sub.3, and
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05]CO.sub.3.
4. The method of claim 1, wherein each of the salt of nickel, the
salt of manganese, the salt of cobalt, and the salt of aluminium
independently comprise an anion selected from the group consisting
of sulfate, nitrate, acetate, chloride, and combinations
thereof.
5. The method of claim 1, wherein the salt of the aluminium is
sodium aluminate.
6. The method of claim 1, wherein the precipitating agent is
selected from the group consisting of sodium hydroxide, potassium
hydroxide, calcium hydroxide, ammonium hydroxide, sodium carbonate,
potassium carbonate, sodium hydrogencarbonate, potassium
hydrogencarbonate, calcium hydrogencarbonate, ammonium carbonate,
and combinations thereof.
7. The method of claim 1, wherein the static mixer has a length
from about 30 cm to about 100 cm and a diameter from about 5 mm to
about 20 cm, and wherein the ratio of the length of the static
mixer to the diameter of the static mixer is from about 2:1 to
about 20:1.
8. The method of claim 1, wherein the static mixer is made of
plastic selected from the group consisting of polypropylene,
polytetrafluoroethylene, polyvinyl chloride, copolymers thereof,
and combinations thereof.
9. The method of claim 1, wherein the static mixer is coupled to a
heating element, and wherein the heating element is a heating
jacket surrounding at least a portion of the length of the static
mixer.
10. The method of claim 9, wherein the temperature of the heating
jacket and the pre-heated first and second solutions are the
same.
11. The method of claim 1, wherein the static mixer is sonicated by
an ultrasonicator.
12. The method of claim 11, wherein the ultrasonicator is operated
at a power from about 60 W to about 600 W.
13. The method of claim 1, wherein the pH value of the
co-precipitating solution in the static mixer is maintained at a
range from about 8 to about 12.
14. The method of claim 1, wherein the co-precipitating solution is
mixed in the static mixer for a time period less than 2
minutes.
15. The method of claim 1, wherein the method does not comprise a
step of adding ammonia solution to the pre-heated second solution
or the co-precipitating solution.
16. The method of claim 1, wherein the suspension is washed with
water for a time period from about 30 minutes to about 2 hours.
17. The method of claim 1, wherein the dried cathode material
precursor and the one or more lithium salts are mixed for a time
period from about 30 minutes to about 2 hours.
18. The method of claim 1, wherein the dried cathode material
precursor has a particle size D50 in the range from about 1 .mu.m
to about 12 .mu.m.
19. The method of claim 1, wherein the dried cathode material
precursor has a D90/D10 ratio from about 1.3 to about 2.
20. The method of claim 1, wherein the lithium salt is selected
from the group consisting of lithium hydroxide, lithium carbonate,
lithium fluoride, lithium acetate, lithium oxalate, and
combinations thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 16/313,978, filed Dec. 28, 2018, which is a U.S. national stage
application of the International Patent Application No.
PCT/CN2017/115346, filed Dec. 8, 2017, which claims the benefit of
U.S. Provisional Application No. 62/435,863, filed Dec. 19, 2016,
all of which are incorporated herein by reference in their
entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of batteries. In
particular, this invention relates to methods for preparing cathode
material for lithium-ion batteries.
BACKGROUND OF THE INVENTION
[0003] In the past decades, lithium-ion batteries (LIBs) have been
widely utilized in various applications especially consumer
electronics because of their superior energy density, long cycle
life and discharging capability. LIBs generally include an anode,
an electrolyte, and a cathode that contains lithium in the form of
a lithium-transition metal oxide, such as LiCoO.sub.2, LiNiO.sub.2
and LiMn.sub.2O.sub.4.
[0004] Currently, LIBs mostly utilize metal oxides as cathode
material with LiCoO.sub.2 as the most popular and commercially
successful representative. However, due to the intrinsic material
properties of this cathode material, besides the toxicity and high
material cost of cobalt, further enhancement of performance of LIBs
is also limited. LiNiO.sub.2 is characterized for its high specific
capacity up to 180 mAh/g. But its application is limited to
experimental research because of difficulties in synthesis and
safety concerns due to thermal runaway reaction. LiMn.sub.2O.sub.4
has been considered as a promising cathode material due to its
advantages of high stability and low cost. However, its low charge
capacity and inferior cycling performance, especially under high
temperatures, limit the application of this material.
[0005] In recent years, a multi-element lithium transition metal
oxide such as lithium nickel manganese cobalt oxide (NMC) and
lithium nickel cobalt aluminium oxide (NCA) has been proposed to
replace LiCoO.sub.2. This multi-element transition metal oxide as
cathode material is expected to leverage merits of each component
material and might even prevail in the overall performance, because
of the synergy effect of the three transition metal ions and the
flexibility of composition. Therefore, LiCoO.sub.2 is gradually
replaced by the ternary transition metal oxides especially in
applications that require high energy density.
[0006] The composite transition metal compound may be prepared by
mixing transition metal-containing salts in a desired molar ratio
with a base in an aqueous solution and simultaneously precipitating
two or more types of transition metal elements in the aqueous
solution. The coprecipitation method requires stringent control of
the operating conditions such as pH, temperature and ion
concentration. Variations of these conditions may affect the
average particle diameter, particle diameter distribution, particle
density and composition of the transition metal cathode material
precursor, thereby resulting in poor electrochemical performance of
the LIBs.
[0007] CN Patent Application No. 102903897 A discloses a
preparation method of a spinel lithium nickel manganese oxide
(LiNi.sub.0.5Mn.sub.1.5O.sub.4) cathode material using a static
mixer. The method comprises mixing a cobalt salt solution and a
manganese salt solution to obtain solution A; mixing a carbonate
solution and an ammonia solution to obtain solution B; pumping
solution A and solution B into a static mixer at the same
volumetric flow rate to obtain a suspension; aging the suspension
for 1 hour to 4 hours; performing washing to obtain a slurry;
spray-drying the slurry to obtain a nickel manganese composite
carbonate precursor; calcining the precursor at 400.degree. C. to
500.degree. C. for 5 hours to 10 hours to obtain a nickel manganese
composite oxide; mixing the composite oxide with lithium salt by a
ball mill; calcining the mixture at 800.degree. C. to 950.degree.
C. However, this method is not suitable for preparing ternary
composite oxide and is only limited to preparing spinel lithium
nickel manganese oxide.
[0008] CN Patent No. 101229928 B discloses a method for preparing a
lithium nickel manganese cobalt oxide cathode material. The method
comprises preparing a mixed aqueous solution of a nickel salt,
cobalt salt and manganese salt in a molar ratio of 1:1:1; preparing
a carbonate aqueous solution; preparing an ammonium aqueous
solution; pumping the three solutions into a stirred reactor and
controlling the pH value in a range between 7.9 and 8.5 to form a
precursor; separating, washing and drying the precursor to obtain
composite carbonate of nickel, manganese and cobalt; calcining the
composite carbonate from 480.degree. C. to 550.degree. C. for 4
hours to 6 hours; ball milling a mixture of lithium salt and water
for 3 hours to 4 hours to prepare a lithium salt slurry; mixing the
lithium salt slurry with the heat-treated precursor to obtain a
mixture; calcining the mixture to obtain the cathode material.
However, conventional mixing in a stirred reactor may lead to
incomplete mixing of reactants because of imperfect macro-mixing.
When a reaction product is precipitated during co-precipitation,
imperfect mixing may have serious consequences, leading to
agglomeration, formation of composite precursor having a wide range
of different particle sizes, and formation of unwanted composite
precursors.
[0009] CN Patent Application No. 103178257 A discloses a method for
preparing an NMC cathode material precursor for lithium-ion
batteries. The method comprises dissolving a nickel salt, a cobalt
salt and a manganese salt in deionized water to obtain a metal salt
solution; preparing an aqueous alkaline solution; mixing the two
solutions and controlling the pH value in a range from 8 to 11 to
obtain a mixture; stirring the mixture for over 60 hours; leaving
the mixture to stand for 2 hours to 4 hours; filtering and
obtaining a solid; washing and drying the solid to obtain the
cathode precursor. However, the method is time-consuming as a very
long time is required for the co-precipitation process. In
addition, the method does not provide sufficient data for
evaluating the electrochemical performance of the cathode
material.
[0010] CN Patent No. 100583512 C discloses a method for preparing
an NCA cathode material. The method comprises preparing a mixed
metal salt solution of a nickel salt, a cobalt salt and an
aluminium salt in a molar ratio of 80:15:5; preparing an alkaline
solution comprising sodium hydroxide and a complexing agent;
pumping the two solutions into a reactor containing a carbonate
solution and controlling the pH value in a range between 9 and 13;
stirring the solution for 20 hours to 30 hours to obtain a cathode
precursor; filtering, washing and drying the precursor; mixing the
precursor with a lithium source to obtain a mixture; calcining the
mixture at a temperature between 700.degree. C. and 900.degree. C.
for 20 hours to 30 hours to obtain the cathode material. However,
the method is also time-consuming since a very long time is
required for the whole process. In addition, conventional mixing in
a stirred reactor may lead to incomplete mixing of reactants
because of imperfect macro-mixing.
[0011] In view of the above, there is always a need to develop a
method for preparing a ternary transition metal oxide as a cathode
material for lithium-ion batteries with good electrochemical
performance with a simple and fast method.
SUMMARY OF THE INVENTION
[0012] The aforementioned needs are met by various aspects and
embodiments disclosed herein.
[0013] In one aspect, provided herein is a method of preparing a
cathode material, comprising the steps of:
[0014] 1) dissolving a combination of at least three of a salt of
nickel, a salt of manganese, a salt of cobalt, and a salt of
aluminium in water to obtain a first solution, wherein a total
molar concentration of the metal elements in the first solution is
from about 0.1 mol/L to about 3 mol/L;
[0015] 2) dissolving a precipitating agent in water to form a
second solution, wherein a concentration of the precipitating agent
in the second solution is from about 0.5 mol/L to about 6
mol/L;
[0016] 3) pre-heating the first solution and the second solution to
the same temperature from about 30.degree. C. to about 80.degree.
C. to obtain a pre-heated first solution and a pre-heated second
solution respectively;
[0017] 4) feeding the pre-heated first solution and the pre-heated
second solution to a first inlet and a second inlet of a static
mixer respectively to obtain a co-precipitating solution;
[0018] 5) filtering a suspension eluted from an outlet of the
static mixer to obtain a cathode material precursor, wherein the
outlet of the static mixer is coupled to a pH controller for
controlling the flow rate of the pre-heated first and second
solutions;
[0019] 6) washing the cathode material precursor with water;
[0020] 7) drying the cathode material precursor at a temperature
from about 60.degree. C. to about 105.degree. C. for a time period
from about 4 hours to about 24 hours to obtain a dried cathode
material precursor;
[0021] 8) mixing the dried cathode material precursor with one or
more lithium salts to obtain a solid mixture, wherein a molar ratio
of the metal element lithium of the one or more lithium salts to
the total amount of the metal elements selected from a combination
of at least three of nickel, manganese, cobalt, and aluminium is
from about 1.5:1 to about 1:1, or from about 1.03:1 to about 1:1;
and
[0022] 9) calcining the solid mixture in two stages to obtain the
cathode material, wherein the first stage is conducted at a
temperature from about 350.degree. C. to about 550.degree. C. for a
time period from about 2 hours to about 10 hours, and the second
stage is conducted at a temperature from about 750.degree. C. to
about 950.degree. C. for a time period from about 6 hours to about
15 hours, and wherein the cathode material comprises a lithium
multi-metal composite oxide represented by
xLi.sub.2MnO.sub.3.(1-x)LiNi.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)O.sub.2-
, wherein 0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1, and 0.ltoreq.x<1; and the cathode material has a
D90/D10 ratio from about 1.4 to about 1.9.
[0023] In some embodiments, each of the salt of nickel, the salt of
manganese, the salt of cobalt, and the salt of the aluminium
independently comprise an anion selected from the group consisting
of sulfate, nitrate, acetate, chloride, and combinations thereof.
In certain embodiments, the salt of the aluminium is sodium
aluminate.
[0024] In certain embodiments, the precipitating agent is selected
from the group consisting of sodium hydroxide, potassium hydroxide,
calcium hydroxide, ammonium hydroxide, sodium carbonate, potassium
carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate,
calcium hydrogencarbonate, ammonium carbonate, and combinations
thereof. In some embodiments, the method does not comprise a step
of adding ammonia solution to the pre-heated second solution or the
co-precipitating solution.
[0025] In some embodiments, the static mixer has a length from
about 30 cm to about 100 cm and a diameter from about 5 mm to about
20 cm. In certain embodiments, the ratio of the length of the
static mixer to the diameter of the static mixer is from about 2:1
to about 20:1. In some embodiments, the static mixer is made of
plastic selected from the group consisting of polypropylene,
polytetrafluoroethylene, polyvinyl chloride, copolymers thereof,
and combinations thereof.
[0026] In certain embodiments, the static mixer is coupled to a
heating element, and wherein the heating element is a heating
jacket surrounding at least a portion of the length of the static
mixer. In some embodiments, the temperature of the heating jacket
and the pre-heated first and second solutions are the same.
[0027] In some embodiments, the static mixer is sonicated by an
ultrasonicator. In certain embodiments, the ultrasonicator is
operated at a power from about 60 W to about 600 W.
[0028] In certain embodiments, the pH value of the co-precipitating
solution in the static mixer is maintained at a range from about 8
to about 12. In some embodiments, the co-precipitating solution is
mixed in the static mixer for a time period less than 2 minutes. In
certain embodiments, the suspension is washed with water for a time
period from about 30 minutes to about 2 hours.
[0029] In some embodiments, the cathode material precursor is
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)](OH).sub.2 or
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)]CO.sub.3, wherein
0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1, and
a+b+c.ltoreq.1. In certain embodiments, the cathode material
precursor is selected from the group consisting of
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33](OH).sub.2,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2](OH).sub.2,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2](OH).sub.2,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2](OH).sub.2,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15](OH).sub.2,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1](OH).sub.2,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04](OH).sub.2,
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05](OH).sub.2,
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33]CO.sub.3,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2]CO.sub.3,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2]CO.sub.3,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2]CO.sub.3,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15]CO.sub.3,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1]CO.sub.3,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04]CO.sub.3, and
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05]CO.sub.3. In some embodiments,
the dried cathode material precursor has a particle size D50 in the
range from about 1 .mu.m to about 12 .mu.m. In certain embodiments,
the dried cathode material precursor has a D90/D10 ratio from about
1.3 to about 2.
[0030] In certain embodiments, the dried cathode material precursor
and the one or more lithium salts are mixed for a time period from
about 30 minutes to about 2 hours. In some embodiments, the lithium
salt is selected from the group consisting of lithium hydroxide,
lithium carbonate, lithium fluoride, lithium acetate, lithium
oxalate, and combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 depicts an embodiment of an apparatus comprising a
static mixer used in the method disclosed herein.
[0032] FIG. 2 depicts a SEM image of the surface morphology of the
cathode material of Example 4.
DETAILED DESCRIPTION OF THE INVENTION
[0033] Provided herein is a method of preparing a cathode material
for a lithium-ion battery cell, comprising the steps of:
[0034] 1) dissolving a combination of at least three of a salt of
nickel, a salt of manganese, a salt of cobalt, and a salt of
aluminium in water to obtain a first solution, wherein a total
molar concentration of the metal elements in the first solution is
from about 0.1 mol/L to about 3 mol/L;
[0035] 2) dissolving a precipitating agent in water to form a
second solution, wherein a concentration of the precipitating agent
in the second solution is from about 0.5 mol/L to about 6
mol/L;
[0036] 3) pre-heating the first solution and the second solution to
the same temperature from about 30.degree. C. to about 80.degree.
C. to obtain a pre-heated first solution and a pre-heated second
solution respectively;
[0037] 4) feeding the pre-heated first solution and the pre-heated
second solution to a first inlet and a second inlet of a static
mixer respectively to obtain a co-precipitating solution;
[0038] 5) filtering a suspension eluted from an outlet of the
static mixer to obtain a cathode material precursor, wherein the
outlet of the static mixer is coupled to a pH controller for
controlling the flow rate of the pre-heated first and second
solutions;
[0039] 6) washing the cathode material precursor with water;
[0040] 7) drying the cathode material precursor at a temperature
from about 60.degree. C. to about 105.degree. C. for a time period
from about 4 hours to about 24 hours to obtain a dried cathode
material precursor;
[0041] 8) mixing the dried cathode material precursor with one or
more lithium salts to obtain a solid mixture, wherein a molar ratio
of the metal element lithium of the one or more lithium salts to
the total amount of the metal elements selected from a combination
of at least three of nickel, manganese, cobalt, and aluminium is
from about 1.5:1 to about 1:1, or from about 1.03:1 to about 1:1;
and
[0042] 9) calcining the solid mixture in two stages to obtain the
cathode material, wherein the first stage is conducted at a
temperature from about 350.degree. C. to about 550.degree. C. for a
time period from about 2 hours to about 10 hours, and the second
stage is conducted at a temperature from about 750.degree. C. to
about 950.degree. C. for a time period from about 6 hours to about
15 hours, and wherein the cathode material comprises a lithium
multi-metal composite oxide represented by
xLi.sub.2MnO.sub.3.(1-x)LiNi.sub.aMn.sub.bC.sub.cAl.sub.(1-a-b-c)O.sub.2,
wherein 0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1, and 0.ltoreq.x<1; and the cathode material has a
D90/D10 ratio from about 1.4 to about 1.9.
[0043] The term "ternary cathode material" refers to a lithium
multi-metal composite oxide comprising lithium and three metal
elements different from lithium. Some non-limiting examples of the
ternary cathode material include lithium nickel manganese cobalt
oxide and lithium nickel cobalt aluminium oxide.
[0044] The term "precipitating agent" refers to a base used in a
precipitating reaction for forming an insoluble solid (precipitate)
by exchanging soluble ion materials. The pH at which a precipitate
is formed depends on the composition of the precipitate. In some
embodiments, the pH is greater than 7.0, greater than 7.5, greater
than 8.0, greater than 9.0, greater than 10.0, greater than 11.0,
or greater than 12.0. In other embodiments, the pH is less than
12.0, less than 11.0, less than 10.0, less than 9.0, or less than
8.0.
[0045] The term "base" includes any molecule or ion that can accept
protons from any proton donor, and/or contain completely or
partially displaceable OH.sup.- ions. Some non-limiting examples of
suitable bases include alkali metal hydroxides (e.g., NaOH, LiOH
and KOH), alkaline earth metal hydroxides (e.g., Ca(OH).sub.2), an
ammonia solution (e.g., NH.sub.4OH), alkali metal carbonates (e.g.,
Na.sub.2CO.sub.3 and K.sub.2CO.sub.3), alkali metal hydrogen
carbonates (e.g., NaHCO.sub.3 and KHCO.sub.3), organic base (e.g.,
(CH.sub.3).sub.4NOH and polyethylene glycol) and mixtures
thereof.
[0046] The term "complexing agent" refers to a molecule that is
chemically bonded to a metal coordination centre to form a
coordination complex.
[0047] The term "static mixer" refers to an apparatus comprising a
conduit or tube and a number of stationary or static mixing
elements arranged in a series within a conduit or pipe that mixes
or blends materials flowing through the conduit by repetitively
combining, dividing and recombining the flow many times. The number
of static mixing elements can range from 4 to 32 or more depending
upon the degree of mixing required and characteristics of materials
being mixed.
[0048] The term "element" refers to a plate inserted in the conduit
that interrupts and divides and recombines the fluid flow.
[0049] The term "heating jacket" refers to a cylindrical jacket
adapted to be placed around an article to be heated.
[0050] The term "calcining" refers to a heat treatment process
whereby a material or a mixture of materials is heated to a high
temperature at which heat-induced physical or chemical change takes
place.
[0051] The term "average particle size D50" refers to a
volume-based accumulative 50% size (D50) which is a particle size
at a point of 50% on an accumulative curve when the accumulative
curve is drawn so that a particle size distribution is obtained on
the volume basis and the whole volume is 100%. Further, with
respect to the cathode material precursor and lithium-containing
composite oxide of the present invention, the average particle size
D50 means a volume-averaged particle size of secondary particles
which are formed by mutual agglomeration and sintering of primary
particles, and in a case where the particles are composed of the
primary particles only, it means a volume-averaged particle size of
the primary particles. Furthermore, D10 means a volume-based
accumulative 10% size, and D90 means a volume-based accumulative
90% size.
[0052] The term "tapped density" refers to the bulk density of the
powder or granules after a compaction process, i.e. density at
constant volume. For example, a vessel containing a loose powdered
sample is mechanically tapped on its surface to compact the sample
to constant volume.
[0053] The term "homogenizer" refers to an equipment that can be
used for homogenization of materials. Any conventional homogenizers
can be used for the method disclosed herein. Some non-limiting
examples of the homogenizer include stirring mixers, blenders,
mills (e.g., colloid mills and sand mills), ultrasonicators,
atomizers, rotor-stator homogenizers, and high pressure
homogenizers.
[0054] The term "ultrasonicator" refers to an equipment that can
apply ultrasound energy to agitate particles in a sample. Any
ultrasonicator that can be coupled to a static mixer can used
herein.
[0055] The term "planetary mixer" refers to an equipment that can
be used to mix or stir different materials, which consists of
blades conducting a planetary motion within a vessel. In some
embodiments, the planetary mixer comprises at least one planetary
blade and at least one high speed dispersion blade. The planetary
and the high speed dispersion blades rotate on their own axes and
also rotate continuously around the vessel. The rotation speed can
be expressed in unit of rotations per minute (rpm) which refers to
the number of rotations that a rotating body completes in one
minute.
[0056] The term "furnace" refers to a device used for
high-temperature heating.
[0057] The term "overs" refers to oversized particles that cannot
pass through the screen.
[0058] The term "unders" refers to particles having a mesh size
smaller than the mesh size of a mesh sieve.
[0059] The term "current collector" refers to a support for coating
the active battery electrode material and a chemically inactive
high electron conductor for keeping an electric current flowing to
electrodes during discharging or charging a secondary battery.
[0060] The term "electrode" refers to a "cathode" or an
"anode."
[0061] The term "positive electrode" is used interchangeably with
cathode. Likewise, the term "negative electrode" is used
interchangeably with anode.
[0062] The term "room temperature" refers to indoor temperatures
from about 18.degree. C. to about 30.degree. C., e.g., 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.degree. C. In some
embodiments, room temperature refers to a temperature of about
20.degree. C.+/-1.degree. C. or +/-2.degree. C. or +/-3.degree. C.
In other embodiments, room temperature refers to a temperature of
about 22.degree. C. or about 25.degree. C.
[0063] The term "C rate" refers to the charging or discharging rate
of a cell or battery, expressed in terms of its total storage
capacity in Ah or mAh. For example, a rate of 1 C means utilization
of all of the stored energy in one hour; a 0.1 C means utilization
of 10% of the energy in one hour or the full energy in 10 hours;
and a 5 C means utilization of the full energy in 12 minutes.
[0064] The term "battery cycle life" refers to the number of
complete charge/discharge cycles a battery can perform before its
nominal capacity falls below 80% of its initial rated capacity.
[0065] The term "ampere-hour (Ah)" refers to a unit used in
specifying the storage capacity of a battery. For example, a
battery with 1 Ah capacity can supply a current of one ampere for
one hour or 0.5 A for two hours, etc. Therefore, 1 Ampere-hour (Ah)
is the equivalent of 3,600 coulombs of electrical charge.
Similarly, the term "miniampere-hour (mAh)" also refers to a unit
of the storage capacity of a battery and is 1/1,000 of an
ampere-hour.
[0066] In the following description, all numbers disclosed herein
are approximate values, regardless whether the word "about" or
"approximate" is used in connection therewith. They may vary by 1
percent, 2 percent, 5 percent, or, sometimes, 10 to 20 percent.
Whenever a numerical range with a lower limit, R.sup.L, and an
upper limit, R.sup.U, is disclosed, any number falling within the
range is specifically disclosed. In particular, the following
numbers within the range are specifically disclosed:
R=R.sup.L.+-.k*(R.sup.U-R.sup.L), wherein k is a variable ranging
from 1 percent to 100 percent with a 1 percent increment, i.e., k
is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . ,
50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent,
97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed.
[0067] FIG. 1 shows an embodiment of the apparatus comprising a
static mixer for preparing a cathode material precursor according
to the present invention. The apparatus disclosed herein comprises
a static mixer 1 having a hollow housing 1a, a first inlet opening
1b through which the pre-heated first solution is introduced into
the static mixer 1 for being mixed there, a second inlet opening 1c
through which the pre-heated second solution is introduced into the
static mixer 1 for being mixed there, a plurality of mixing
elements 1d which are arranged in the static mixer 1, and an outlet
opening 1e for discharging the suspension. The static mixer 1 is
coupled to a heating jacket 2, a pH controller 3 for controlling
the pH of the co-precipitating (CoP) solution; and an
ultrasonicator 4.
[0068] The conventional method of manufacturing multi-element
cathode material precursor comprises reacting an alkaline aqueous
solution, such as sodium hydroxide, with an aqueous solution of
metal salts to precipitate composite metal hydroxide in a stirring
tank. After the growth of the crystal by aging the precipitate, the
metal hydroxide crystal is filtered. However, poor mixing may
result in formation of dead zones or stagnant region. This effect
always occurs in heterogeneous systems (e.g. suspensions and
emulsions). In an incompletely mixed state, local concentration
differences exist. Therefore, there is no guarantee that uniformity
of composition of the precipitate is achieved. Furthermore, the
co-precipitation method with stirring condition usually requires a
long mixing time to fully precipitate and the particles thus formed
may agglomerate. This may lead to the formation of composite metal
hydroxide powder having non-uniform particle size distribution,
thereby making it difficult to provide an electrode of high packing
density.
[0069] The method disclosed herein comprises mixing a mixed
nickel/manganese/cobalt salt solution or a mixed
nickel/cobalt/aluminium salt solution with a solution having a
dissolved precipitating agent in a static mixer to prepare a
ternary cathode material precursor. The two solutions are fed into
the static mixer continuously and mixed together by the static
mixing elements as the fluid stream passes over each mixing
element. Static mixers can provide uniform mixing in a relatively
short period of time.
[0070] The invention is particularly suitable for preparing ternary
composite and cathode materials with high nickel content. In some
embodiments, the ternary composite is a lithium multi-metal
composite oxide represented by
xLi.sub.2MnO.sub.3.(1-x)LiNi.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)O.sub.2-
, wherein 0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1,
a+b+c.ltoreq.1, and 0.ltoreq.x<1. In certain embodiments, the
ternary composite is a LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2
(NMC333), LiNi.sub.0.4Mn.sub.0.4Co.sub.0.2O.sub.2,
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2 (NMC532),
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2 (NMC622),
LiNi.sub.0.7Mn.sub.0.15Co.sub.0.15O.sub.2,
LiNi.sub.0.5Mn.sub.0.1Co.sub.0.1O.sub.2 (NMC811),
LiNi.sub.0.92Mn.sub.0.04Co.sub.0.04O.sub.2,
LiNi.sub.0.8Co.sub.0.15Al.sub.0.15O.sub.2 (NCA),
0.4Li.sub.2MnO.sub.3.0.6LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2,
0.3Li.sub.2MnO.sub.3.0.7LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2,
or
0.16Li.sub.2MnO.sub.3.0.84LiNi.sub.0.4Co.sub.0.4Mn.sub.0.2O.sub.2.
[0071] The production of ternary cathode material precursor with
high nickel content such as
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1](OH).sub.2 and
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05](OH).sub.2 is more difficult than
mono- and bi-metallic cathode materials with conventional mixing
method.
[0072] In some embodiments, the first solution is prepared by
dissolving a combination of at least three of a salt of nickel, a
salt of manganese, a salt of cobalt, and a salt of aluminium in
water at any temperature that is suitable for dissolution. Each of
the salt of nickel, the salt of manganese, the salt of cobalt, and
the salt of aluminium disclosed herein can independently include an
anion selected from the group consisting of sulfate, nitrate,
acetate, chloride and combinations thereof. Some non-limiting
examples of the salt of nickel include nickel sulfate, nickel
nitrate, nickel acetate and nickel chloride. Some non-limiting
examples of the salt of manganese include manganese sulfate,
manganese acetate and manganese chloride. Some non-limiting
examples of the salt of cobalt include cobalt sulfate, cobalt
nitrate, cobalt acetate and cobalt chloride. Some non-limiting
examples of the salt of aluminium include aluminium sulfate,
aluminium nitrate, aluminium acetate, aluminium chloride, and
sodium aluminate.
[0073] In certain embodiments, the concentration of each of the
salt of nickel, the salt of manganese, the salt of cobalt, and the
salt of aluminium in the aqueous solution can be independently any
concentration as long as it does not excess the critical saturated
concentration. In some embodiment, a total molar concentration of
the metal elements in the first solution is from about 0.1 mol/L to
about 5 mol/L, from about 0.1 mol/L to about 4 mol/L, from about
0.1 mol/L to about 3 mol/L, from about 0.1 mol/L to about 2 mol/L,
from about 0.1 mol/L to about 1 mol/L, or from about 1 mol/L to
about 3 mol/L.
[0074] In some embodiments, the mole fractions of each of the salt
of nickel, the salt of cobalt, the salt of manganese, and the salt
of aluminium in the first solution are independently from about 0
to about 1, from about 0 to about 0.9, from about 0 to about 0.8,
from about 0 to about 0.7, from about 0 to about 0.6, from about 0
to about 0.5, from about 0 to about 0.4, from about 0 to about 0.3,
from about 0 to about 0.2, from about 0 to about 0.1, from about 0
to about 0.05, or from about 0 to about 0.04.
[0075] In some embodiments, the mole fraction of the salt of nickel
in the first suspension is greater than or equal to the mole
fraction of the salt of cobalt, the salt of manganese and/or the
salt of aluminium, or the total mole fraction of the salt of metal
other than nickel in the first suspension. In certain embodiments,
the mole fraction of the salt of nickel in the first solution is
from about 0 to about 1, from about 0.3 to about 0.92, from about
0.3 to about 0.9, or from about 0.5 to about 0.8. In some
embodiments, the mole fraction of the salt of nickel in the first
solution is greater than 0.33, greater than 0.5, greater than 0.6,
greater than 0.8, or greater than 0.9. In certain embodiments, the
mole fraction of the salt of nickel in the first solution is about
0.33, about 0.5, about 0.6, about 0.8, about 0.9, or about
0.92.
[0076] In some embodiments, the mole fraction of each of the salt
of cobalt and the salt of manganese in the first solution is
independently from about 0 to about 1, from about 0 to about 0.5,
from about 0 to about 0.33, from about 0 to about 0.2, or from
about 0 to about 0.1. In certain embodiments, the mole fraction of
each of the salt of cobalt and the salt of manganese in the first
solution is independently about 0.33, about 0.2, about 0.1, about
0.05, or about 0.04.
[0077] In certain embodiments, the mole fraction of the salt of
aluminium in the first solution is from about 0 to about 1, from
about 0 to about 0.2, or from about 0 to about 0.1. In some
embodiments, the mole fraction of the salt of aluminium in the
first solution is less than 0.2, less than 0.1, less than 0.05, or
less than 0.03. In certain embodiment, the mole fraction of the
salt of aluminium in the first solution is about 0.2, about 0.1, or
about 0.05.
[0078] In some embodiments, the molar ratio of the salt of
nickel:the salt of manganese:the salt of cobalt is about 1:1:1,
about 5:3:2, about 6:2:2, about 8:1:1, about 9:0.5:0.5, or about
9.2:0.4:0.4. In certain embodiments, the molar ratio of the salt of
nickel:the salt of cobalt:the salt of aluminium is about
8:1.5:0.15.
[0079] In certain embodiments, the second solution is prepared by
dissolving a precipitating agent in water. Some non-limiting
examples of the precipitating agent include sodium hydroxide,
potassium hydroxide, calcium hydroxide, ammonium hydroxide, sodium
carbonate, potassium carbonate, sodium hydrogencarbonate, potassium
hydrogencarbonate, calcium hydrogencarbonate, and ammonium
carbonate.
[0080] In some embodiments, the concentration of the precipitating
agent in the second solution is from about 0.5 mol/L to about 8
mol/L, from about 0.5 mol/L to about 6 mol/L, from about 0.5 mol/L
to about 4 mol/L, or from about 0.5 mol/L to about 2 mol/L.
[0081] The first and second solutions are pre-heated before feeding
into the static mixer. One of the important conditions for the
co-precipitation reaction is the pre-heating temperature, which
affects the quality and uniformity of the cathode material
precursor. In some embodiments, each of the first and second
solutions are independently pre-heated to the same temperature from
about 30.degree. C. to about 80.degree. C., from about 40.degree.
C. to about 80.degree. C., from about 50.degree. C. to about
80.degree. C., from about 60.degree. C. to about 80.degree. C., or
from about 70.degree. C. to about 80.degree. C. In certain
embodiments, each of the first and second solutions are
independently pre-heated to the same temperature greater than
30.degree. C., greater than 40.degree. C., greater than 50.degree.
C., or greater than 60.degree. C. In some embodiments, each of the
first and second solutions are independently pre-heated to the same
temperature at about 30.degree. C., about 40.degree. C., about
50.degree. C., about 60.degree. C., about 70.degree. C., or about
80.degree. C.
[0082] The pre-heated first solution and the pre-heated second
solution are fed to a first inlet and a second inlet of a static
mixer respectively to obtain a co-precipitating solution. Any
static mixer that can be used to mix the two solutions can be used
herein. The mixing element located in the flow path divides and
recombines the feed materials. In some embodiments, the mixing
element has a helical structure. The rotation and deflection of the
co-precipitating solution along the helical paths provides a
thorough mixing of the solution. These spiralling flow paths
provide the desired rotation and mixing of materials and are
particularly effective for mixing along circular conduits. The
housing and/or mixing elements of the static mixer can be made of
corrosion resistant plastics selected from the group consisting of
polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinyl
chloride (PVC), copolymers thereof, and combinations thereof.
[0083] The pH of the co-precipitating solution is crucial to the
formation of ternary cathode material precursor as co-precipitation
that occurs over a narrow pH range can ensure formation of
desirable composition of the cathode material precursor.
Conventional methods of preparing a cathode material precursor
comprise adding ammonia solution or ethylenediamine to the second
solution or adding a third solution having ammonia or
ethylenediamine to the co-precipitating solution to control the pH
of the co-precipitating solution. However, this often leads to a
significant change of pH (e.g., .gtoreq.1 unit) throughout the
process and the use of additional chemical increases the complexity
of the preparation process. In the present invention, an automatic
pH controller is coupled to the outlet of the static mixer to
measure the pH of the co-precipitating solution. The automatic pH
controller controls the flow rate of the pre-heated first solution
and the pre-heated second solution fed into the static mixer
according to the measured pH of the co-precipitating solution,
thereby maintaining a constant pH of the co-precipitating solution.
Therefore, a narrow pH range can be maintained with the help of an
automatic pH controller.
[0084] In some embodiments, the pH of the co-precipitating solution
is from about 8 to about 12, from about 8 to about 11, from about 8
to about 10, from about 8 to about 9, from about 9 to about 12,
from about 9 to about 11, from about 9 to about 10, from about 10
to about 12, from about 10 to about 11, from about 8.5 to about
9.5, from about 9.5 to about 10.5, or from about 10.5 to about
11.5. In certain embodiments, the pH of the co-precipitating
solution is less than 12, less than 11.5, less than 11, less than
10.5, less than 10, less than 9.5, less than 9, or less than 8.5.
In some embodiments, the pH of the co-precipitating solution is
greater than 8, greater than 8.5, greater than 9, greater than 9.5,
greater than 10, greater than 10.5, greater than 11, or greater
than 11.5. In certain embodiments, the pH of the co-precipitating
solution is about 8, about 8.5, about 9, about 10, about 10.5,
about 11, about 11.5, or about 12. In some embodiments, the change
of the pH of the co-precipitating solution is less than 1 pH unit,
less than 0.8 pH unit, less than 0.6 pH unit, less than 0.4 pH
unit, or less than 0.2 pH unit.
[0085] In certain embodiments, the pH controller comprises two
pumps for pumping the pre-heated first solution and the pre-heated
second solution into the static mixer. Some non-limiting examples
of the pump include tubular diaphragm pumps, bellows pumps,
peristaltic pump and diaphragm pumps. In some embodiments, each of
the flow rates of the pre-heated first solution and the pre-heated
second solution feeding into the static mixer is independently from
about 6 L/hour to about 100 L/hour, from about 6 L/hour to about 80
L/hour, from about 6 L/hour to about 60 L/hour, from about 6 L/hour
to about 40 L/hour, from about 6 L/hour to about 20 L/hour, or from
about 6 L/hour to about 10 L/hour. In some embodiments, each of the
flow rates of the pre-heated first solution and the pre-heated
second solution feeding into the static mixer is independently
greater than 5 L/hour, greater than 10 L/hour, greater than 15
L/hour, or greater than 20 L/hour.
[0086] In some embodiments, the pre-heated second solution or the
co-precipitating solution is free of ammonia or ethylenediamine. In
certain embodiments, the method of the present invention does not
comprise a step of adding ammonia solution or ethylenediamine to
the pre-heated second solution or the co-precipitating
solution.
[0087] Since pH variation may affect the formation and quality of
the cathode material precursor, the pH of the co-precipitating
solution is monitored and regulated continuously during the
operation of the static mixer. The volume of the static mixer
should not be too large since there will be a delay of pH
adjustment. The length of the static mixer is measured in the axial
direction of the static mixer. The diameter of the static mixer is
the internal diameter of the static mixer. The static mixer has a
uniform circular cross-section along the length of the static
mixer. In some embodiments, the length of the static mixer is from
about 30 cm to about 100 cm, from about 30 cm to about 80 cm, from
about 30 cm to about 60 cm, from about 30 cm to about 40 cm, from
about 50 cm to about 100 cm, from about 50 cm to about 80 cm, or
from about 50 cm to about 60 cm. In certain embodiments, the
diameter of the static mixer is from about 1 mm to about 25 cm,
from about 5 mm to about 20 cm, from about 5 mm to about 15 cm,
from about 5 mm to about 10 cm, from about 5 mm to about 5 cm, from
about 5 cm to about 20 cm, or from about 5 cm to about 15 cm. In
some embodiments, the length of the static mixer is longer than the
diameter of the static mixer. In some embodiments, the ratio of the
length of the static mixer to the diameter of the static mixer is
from about 2:1 to about 20:1, from about 5:1 to about 20:1, from
about 10:1 to about 20:1, or from about 15:1 to about 20:1. In
certain embodiments, the ratio of the length of the static mixer to
the diameter of the static mixer is less than 20:1, less than 15:1,
less than 10:1, or less than 5:1. In certain embodiments, the ratio
of the length of the static mixer to the diameter of the static
mixer is greater than 2:1, greater than 5:1, greater than 10:1, or
greater than 15:1.
[0088] The static mixer of the present invention can be applied in
any orientation. In some embodiments, the static mixer can be
positioned horizontally or vertically. In certain embodiments, the
static mixer can be operated in an inclined position.
[0089] In certain embodiments, the static mixer is coupled to a
heating element surrounding at least a portion of the length of the
static mixer. In some embodiments, the heating element is a heating
jacket. In certain embodiments, the static mixer is heated by the
heating jacket to the same temperature as the pre-heated first
solution and the pre-heated second solution to maintain a constant
temperature during co-precipitation. In this way, the
co-precipitating solution in the static mixer can be at the same
temperature as the pre-heated solutions, thereby reducing the
temperature variation during the formation of cathode material
precursor. In some embodiments, the static mixer is heated to a
temperature from about 30.degree. C. to about 80.degree. C., from
about 40.degree. C. to about 80.degree. C., from about 50.degree.
C. to about 80.degree. C., from about 60.degree. C. to about
80.degree. C., or from about 70.degree. C. to about 80.degree. C.
In certain embodiments, the static mixer is heated by a heating
jacket to a temperature greater than 30.degree. C., greater than
40.degree. C., greater than 50.degree. C., or greater than
60.degree. C.
[0090] The solutions, upon entering the static mixer, has a small
viscosity. After mixing, the viscosity of the co-precipitating
solution increases slowly as the mixture passes through the static
mixer. Solids may accumulate in the static mixer and flow rate will
be reduced, thereby adversely affecting mixing of the
co-precipitating solution and formation of the desired composition
of the cathode material precursor. The operation of the static
mixer has to be ended in order to successfully remove the
accumulated solids in the static mixer. However, this increases the
complexity and lowers the efficiency of the preparation process. In
some embodiments, the static mixer is coupled to an ultrasonicator.
In certain embodiments, the static mixer is sonicated continuously
or intermittently by the ultrasonicator to prevent precipitate from
adhering on the surface of the mixing elements and the static mixer
from becoming clogged during operation. In some embodiments, the
ultrasonicator is operated from about 60 W to about 600 W, from
about 60 W to about 400 W, from about 60 W to about 200 W, or from
about 60 W to about 100 W. The static mixer coupled to an
ultrasonicator allows a continuous mixing operation. Accumulation
of solid from a previous batch is thereby minimized. In some
embodiments, the static mixer can be operated continuously for a
time period of more than 5 hours, more than 10 hours, more than 15
hours, more than 20 hours, more than 24 hours, more than 48 hours,
or more than 72 hours.
[0091] The mixing time of the co-precipitating solution of the
present invention is greatly reduced compared to conventional
mixing method. In some embodiments, the co-precipitating solution
is mixed in the static mixer for a time period from about 10
seconds to about 60 seconds, from about 10 seconds to about 50
seconds, from about 10 seconds to about 40 seconds, from about 20
seconds to about 60 seconds, from about 30 seconds to about 60
seconds, from about 40 seconds to about 60 seconds, or from about
40 seconds to about 50 seconds. In certain embodiments, the
co-precipitating solution is mixed in the static mixer for a time
period less than 2 minutes, less than 1.5 minutes, less than 1
minute, less than 50 seconds, less than 40 seconds, or less than 30
seconds.
[0092] A suspension of cathode material precursor is collected from
the outlet of the static mixer. The suspension is filtered and
washed with water to reduce the alkalinity of the cathode material
precursor. In some embodiments, the suspension is washed with water
for 1 to 5 times, 1 to 4 times, 1 to 3 times, or 1 to 2 times. In
certain embodiments, the suspension is washed for a time period
from about 15 minutes to about 2 hours, from about 15 minutes to
about 1 hour, or from about 15 minutes to about 30 minutes.
[0093] In some embodiments, the cathode material precursor is
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)](OH).sub.2 or
[Ni.sub.aMn.sub.bCo.sub.cAl.sub.(1-a-b-c)]CO.sub.3, wherein
0.ltoreq.a<1, 0.ltoreq.b<1, 0.ltoreq.c<1, and
a+b+c.ltoreq.1. In certain embodiments, a is any number from about
0 to about 1, from about 0.33 to about 0.92, from about 0.33 to
about 0.9, from about 0.33 to about 0.8, from about 0.33 to about
0.6, from about 0.5 to about 0.92, from about 0.5 to about 0.8,
from about 0.6 to about 0.92, or from about 0.6 to about 0.9. In
some embodiments, b and c is independently any number from about
0.01 to about 0.5, from about 0.04 to about 0.5, from about 0.04 to
about 0.4, from about 0.1 to about 0.4, from about 0.1 to about
0.3, or from about 0.2 to about 0.4.
[0094] In certain embodiments, the cathode material precursor is
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33](OH).sub.2,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2](OH).sub.2,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2](OH).sub.2,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2](OH).sub.2,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15](OH).sub.2,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1](OH).sub.2,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04](OH).sub.2,
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05](OH).sub.2,
[Ni.sub.0.33Mn.sub.0.33Co.sub.0.33]CO.sub.3,
[Ni.sub.0.4Mn.sub.0.4Co.sub.0.2]CO.sub.3,
[Ni.sub.0.5Mn.sub.0.3Co.sub.0.2]CO.sub.3,
[Ni.sub.0.6Mn.sub.0.2Co.sub.0.2]CO.sub.3,
[Ni.sub.0.7Mn.sub.0.15Co.sub.0.15]CO.sub.3,
[Ni.sub.0.8Mn.sub.0.1Co.sub.0.1]CO.sub.3,
[Ni.sub.0.92Mn.sub.0.04Co.sub.0.04]CO.sub.3, and
[Ni.sub.0.8Co.sub.0.15Al.sub.0.05]CO.sub.3.
[0095] The cathode material precursor is then dried. Any dryer that
can dry the cathode material precursor can be used herein. Some
non-limiting examples of suitable dryer include a double-cone
vacuum dryer, a microwave dryer, a microwave vacuum dryer, a hot
air dryer, or a spray dryer. In some embodiments, the cathode
material precursor is dried by a microwave dryer or a microwave
vacuum dryer, wherein the dryer is operated at a power from about 5
kW to about 15 kW, from about 6 kW to about 20 kW, from about 7 kW
to about 20 kW, from about 15 kW to about 70 kW, from about 20 kW
to about 90 kW, from about 30 kW to about 100 kW, or from about 50
kW to about 100 kW.
[0096] In other embodiments, the cathode material precursor is
dried by a vacuum dryer, a hot air dryer, or a spray dryer at a
temperature from about 60.degree. C. to about 105.degree. C., from
about 60.degree. C. to about 100.degree. C., from about 60.degree.
C. to about 90.degree. C., from about 60.degree. C. to about
80.degree. C., from about 60.degree. C. to about 70.degree. C.,
from about 70.degree. C. to about 90.degree. C., or from about
70.degree. C. to about 80.degree. C. In some embodiments, the
suspension is dried for a time period from about 4 hours to about
24 hours, from about 4 hours to about 20 hours, from about 4 hours
to about 16 hours, from about 4 hours to about 12 hours, from about
4 hours to about 8 hours, or from about 4 hours to about 6
hours.
[0097] In some embodiments, the dried cathode material precursor
has an average particle size D50 in the range from about 1 .mu.m to
about 12 .mu.m, from about 1 .mu.m to about 10 .mu.m, from about 1
.mu.m to about 8 .mu.m, from about 1 .mu.m to about 6 .mu.m, from
about 1 .mu.m to about 4 .mu.m, from about 1 .mu.m to about 2
.mu.m, from about 5 .mu.m to about 12 .mu.m, from about 5 .mu.m to
about 10 .mu.m, or from about 5 .mu.m to about 8 .mu.m. In certain
embodiments, the dried cathode material precursor has an average
particle size D50 less than 12 .mu.m, less than 10 .mu.m, less than
8 .mu.m, less than 6 .mu.m, less than 4 .mu.m, or less than 2
.mu.m. In some embodiments, the dried cathode material precursor
has an average particle size D50 greater than 1 .mu.m, greater than
2 .mu.m, greater than 4 .mu.m, greater than 6 .mu.m, greater than 8
.mu.m, or greater than 10 .mu.m.
[0098] The method disclosed herein allows sufficiently uniform
mixing of the two solutions in a very short time to obtain a
suspension of uniform quality in a continuous process. In addition,
rapid and uniform mixing of the two solutions gives a cathode
material precursor with controlled composition and good uniformity
in particle size. In some embodiment, the dried cathode material
precursor has a D90/D10 ratio from about 1.2 to about 2.5, from
about 1.2 to about 2.3, from about 1.2 to about 2.1, from about 1.2
to about 2, from about 1.2 to about 1.8, from about 1.3 to about
1.8, from about 1.3 to about 1.7, from about 1.3 to about 1.6, from
about 1.3 to about 1.5, from about 1.3 to about 1.4, from about 1.4
to about 1.8, from about 1.5 to about 1.9, or from about 1.5 to
about 1.8. In certain embodiments, the dried cathode material
precursor has a D90/D10 ratio less than 2.5, less than 2.3, less
than 2.1, less than 2, less than 1.9, less than 1.8, less than 1.7,
less than 1.6, less than 1.5, less than 1.4, or less than 1.3.
[0099] The dried cathode material precursor is then mixed with one
or more lithium salts to obtain a solid mixture in a homogenizer.
Some non-limiting examples of the lithium salts include lithium
hydroxide, lithium carbonate, lithium fluoride, lithium acetate,
and lithium oxalate.
[0100] In certain embodiments, the molar ratio of the metal element
lithium of the one or more lithium salts to the total amount of the
metal elements selected from a combination of at least three of
nickel, manganese, cobalt, and aluminium is 1:1. Addition of excess
lithium salt may lead to the formation of lithium oxide and lithium
carbonate on the surface of the cathode material during
calcination, resulting in poor electrochemical performance. The
rechargeable battery may explode due to increased internal pressure
caused by released gas, such as carbon dioxide.
[0101] In certain embodiments, the number of mole of the metal
element lithium of the one or more lithium salts is greater than or
equal to the total number of mole of the metal elements selected
from a combination of at least three of nickel, manganese, cobalt,
and aluminium. In some embodiments, the molar ratio of the metal
element lithium of the one or more lithium salts to the total
amount of the metal elements selected from a combination of at
least three of nickel, manganese, cobalt, and aluminium is from
about 1:1 to about 1.01:1, from about 1:1 to about 1.02:1, or from
about 1:1 to about 1.03:1. In certain embodiments, the molar ratio
of the metal element lithium of the one or more lithium salts to
the total amount of the metal elements selected from a combination
of at least three of nickel, manganese, cobalt, and aluminium is
less than 1.05:1, less than 1.04:1, less than 1.03:1, less than
1.02:1, or less than 1.01:1. In some embodiments, the molar ratio
of the metal element lithium to the total amount of the metal
elements selected from a combination of at least three of nickel,
manganese, cobalt, and aluminium in a lithium-rich cathode material
is from about 1.5:1 to about 1.1:1, from about 1.5:1 to about
1.2:1, from about 1.5:1 to about 1.3:1, or from about 1.5:1 to
about 1.4:1. In certain embodiments, the molar ratio of the metal
element lithium to the total amount of the metal elements selected
from a combination of at least three of nickel, manganese, cobalt,
and aluminium in a lithium-rich cathode material is greater than
1.1:1, greater than 1.2:1, greater than 1.3:1, or greater than
1.4:1.
[0102] Any homogenizer that can evenly mix the dried cathode
material precursor with the one or more lithium salts to obtain a
solid mixture can be used herein. In some embodiments, homogenizer
may be operated dry without adding any liquid. Some non-limiting
examples of the homogenizer include a blender, a single helix cone
mixer, a double helix cone mixer, a blade mixer, a stirring mixer,
and a ball mill. In some embodiments, the stirring speed of the
homogenizer is from about 5,000 rpm to about 15,000 rpm, from about
5,000 rpm to about 10,000 rpm, from about 5,000 rpm to about 9,000
rpm, from about 5,000 rpm to about 8,000 rpm, from about 5,000 rpm
to about 7,000 rpm, or from about 5,000 rpm to about 6,000 rpm. In
certain embodiments, the solid mixture is homogenized for a time
period from about 0.5 hour to about 3 hours, from about 0.5 hour to
about 2 hours, or from about 0.5 hour to 1 hour.
[0103] In certain embodiments, homogenizer may be operated in the
presence of a solvent or water. The solid mixture can be dispersed
in an aqueous solvent to form a slurry. Some non-limiting examples
of the homogenizer for homogenizing the slurry include a blender, a
stirring mixer, a mill, an ultrasonicator, a rotor-stator
homogenizer, a planetary stirring mixer, a high pressure
homogenizer, and combinations thereof.
[0104] After the mixing step, the solid mixture or the slurry can
be calcined in a furnace or an oven to produce a cathode material.
Any furnace or oven that can calcine the solid mixture or the
slurry can be used herein. In some embodiments, the calcination
process is performed by a furnace. Some non-limiting examples of
the furnace include a box furnace, a push-plate tunnel furnace and
a rotary furnace.
[0105] In some embodiments, the solid mixture or the slurry can be
calcined under atmospheric pressure. In certain embodiments, the
solid mixture can be calcined under an atmosphere with an oxygen
content higher than 21%. In some embodiments, the oxygen content in
the calcining process is at least 22%, at least 25%, at least 30%,
at least 32%, at least 34%, at least 36%, at least 40%, at least
45%, at least 50%, at least 55%, at least 60%, at least 65%, at
least 70%, at least 75%, at least 80%, at least 85%, at least 90%,
at least 95%, or at least 99%. In some embodiments, the oxygen
content in the calcining process is at most 25%, at most 30%, at
most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at
most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at
most 85%, at most 90%, at most 95%, or at most 99%. In certain
embodiments, the oxygen content in the calcining process is 100%.
In general, the reaction time for complete transformation of the
cathode material precursor into the corresponding metal oxide
decreases with increasing oxygen content. In other embodiments, the
solid mixture can be calcined under an inert atmosphere.
[0106] In further embodiments, the furnace comprises an agitation
device which is used for agitating the powdered solids. In still
further embodiments, the agitation device comprises a rotating
blade or paddle.
[0107] Heat transfer in the rotary furnace and furnace equipped
with a stirring apparatus is usually much more efficient than
static furnace because they offer the advantage of providing
agitation to powdered solids. Mechanism of agitation ensures
uniform heating of the powdered solids. This overcomes the problem
of long reaction times often experienced by processing in a box
furnace and hence lowers the operating costs.
[0108] In some embodiments, calcination of the solid mixture or the
slurry is carried out in two stages consisting of a first stage and
a second stage, wherein the temperature of the first stage is lower
than the temperature of the second stage. In the first stage, the
cathode material precursor is converted to the corresponding metal
oxide. In the second stage, the corresponding metal oxide is
converted to the final lithium metal oxide product.
[0109] The temperature in the first stage can be within the range
of 350.degree. C. to 550.degree. C. In some embodiments, the solid
mixture or the slurry is calcined in the first stage at a
temperature from about 350.degree. C. to about 500.degree. C., from
about 350.degree. C. to about 450.degree. C., or from about
350.degree. C. to about 400.degree. C. In certain embodiments, the
solid mixture or the slurry is calcined in the first stage at a
temperature less than 550.degree. C., less than 500.degree. C., or
less than 450.degree. C. In certain embodiments, the solid mixture
or the slurry is calcined in the first stage at a temperature at
about 350.degree. C., about 400.degree. C., about 450.degree. C.,
about 500.degree. C., or about 550.degree. C. In some embodiments,
the solid mixture or the slurry is calcined in the first stage for
a time period from about 2 hours to about 10 hours, from about 2
hours to about 8 hours, from about 2 hours to about 6 hours, or
from about 2 hours to about 4 hours.
[0110] The temperature in the second stage can be within the range
of 750.degree. C. to 950.degree. C. In some embodiments, the solid
mixture is calcined in the second stage at a temperature from about
750.degree. C. to about 900.degree. C., from about 750.degree. C.
to about 850.degree. C., or from about 750.degree. C. to about
800.degree. C. In certain embodiments, the solid mixture is
calcined in the second stage at a temperature greater than
750.degree. C., greater than 800.degree. C., greater than
850.degree. C., or greater than 900.degree. C. In some embodiments,
the solid mixture is calcined in the second stage for a time period
from about 6 hours to about 15 hours, from about 6 hours to about
14 hours, from about 6 hours to about 12 hours, from about 6 hours
to about 10 hours, or from about 6 hours to about 8 hours.
[0111] In some embodiments, a desired temperature can be reached by
gradually increasing the temperature of the furnace. In certain
embodiments, the temperature is increased at a rate from about
1.degree. C./minute to about 10.degree. C./minute, from about
1.degree. C./minute to about 8.degree. C./minute, from about
1.degree. C./minute to about 6.degree. C./minute, from about
1.degree. C./minute to about 4.degree. C./minute, from about
1.degree. C./minute to about 2.degree. C./minute, from about
4.degree. C./minute to about 10.degree. C./minute, from about
4.degree. C./minute to about 8.degree. C./minute, or from about
4.degree. C./minute to about 6.degree. C./minute.
[0112] After the calcining step, the calcined product can be cooled
to room temperature. In some embodiments, the calcined product is
cooled by decreasing the temperature gradually. In certain
embodiments, the temperature of the calcination process is reduced
at a rate from about 1.degree. C./minute to about 5.degree.
C./minute, from about 2.degree. C./minute to about 5.degree.
C./minute, from about 3.degree. C./minute to about 5.degree.
C./minute, from about 2.degree. C./minute to about 6.degree.
C./minute, from about 3.degree. C./minute to about 6.degree.
C./minute, or from about 1.degree. C./minute to about 4.degree.
C./minute.
[0113] In some embodiments, the particles of the calcined product
can be separated by using a screen or a sieve. The material is
placed on the screen and then the screen is shaken to allow the
smaller particles to flow through. The "overs" are the particles
that remain on the screen and the "unders" are the particles that
pass through the screen.
[0114] In certain embodiments, the isolating step is performed by
passing through a mesh sieve having a range from about 200 to about
500. In certain embodiments, the isolating step is performed by
passing through a mesh sieve of about 200, about 300, about 400, or
about 500. In further embodiments, the isolating step can be
performed twice with two sieves of different mesh sizes. The
particles of the calcined product pass through a mesh sieve of the
desired mesh size. The isolated particles of the calcined product
from the first isolating step can then pass through a second mesh
sieve of a smaller mesh to reduce the size of the particles even
further. In still further embodiments, the isolated particles of
the calcined product from the second isolating step can pass
through mesh sieves with mesh sizes that continue to become
smaller.
[0115] In some embodiments, the D50 of the cathode material is from
about 3 .mu.m to about 15 .mu.m, from about 3 .mu.m to about 13
.mu.m, from about 3 .mu.m to about 11 .mu.m, from about 3 .mu.m to
about 9 .mu.m, from about 3 .mu.m to about 7 .mu.m, or from about 3
.mu.m to about 5 .mu.m. In some embodiments, the D50 of the cathode
material is about 3 .mu.m, about 5 .mu.m, about 7 .mu.m, about 9
.mu.m, about 11 .mu.m, about 13 .mu.m, or about 15 .mu.m.
[0116] The cathode material has a uniform particle size and a
D90/D10 ratio of about 1.3 to about 1.9. In some embodiments, the
D90/D10 ratio of the cathode material is from about 1.4 to about
1.9, from about 1.4 to about 1.8, from about 1.4 to about 1.7, from
about 1.4 to about 1.6, or from about 1.4 to about 1.5. In certain
embodiments, the D90/D10 ratio of the cathode material is about
1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, or
about 1.9.
[0117] The cathode material disclosed herein has excellent cycling
properties and overall capacity as a result of a relatively high
tapped density combined with a high specific capacity. In some
embodiments, the tapped density of the cathode material is from
about 1.6 g/cm.sup.3 to about 3 g/cm.sup.3, from about 1.6
g/cm.sup.3 to about 2.8 g/cm.sup.3, from about 1.6 g/cm.sup.3 to
about 2.6 g/cm.sup.3, from about 1.6 g/cm.sup.3 to about 2.4
g/cm.sup.3, from about 1.6 g/cm.sup.3 to about 2.2 g/cm.sup.3, from
about 1.6 g/cm.sup.3 to about 2.0 g/cm.sup.3, or from about 1.6
g/cm.sup.3 to about 1.8 g/cm.sup.3. In certain embodiments, the
tapped density of the cathode material is about 1.6 g/cm.sup.3,
about 1.8 g/cm.sup.3, about 2.0 g/cm.sup.3, about 2.2 g/cm.sup.3,
about 2.4 g/cm.sup.3, about 2.6 g/cm.sup.3, about 2.8 g/cm.sup.3,
or about 3.0 g/cm.sup.3. As a result of the high tapped density and
excellent cycling performance, the battery exhibits continuing high
total capacity when cycled.
[0118] In some embodiments, the second solution or the
co-precipitating solution does not comprise a complexing agent for
the purposes of improving the physical and/or chemical properties
of the cathode material precursor. In certain embodiments, the
method of the present invention does not comprise a step of adding
a complexing agent to the pre-heated second solution or the
co-precipitating solution. Some non-limiting examples of the
complexing agent include ammonia, ethylenediaminetetraacetic acid
(EDTA), and ethylene glycol-bis(.beta.-aminoethyl
ether)-N,N,N',N'-tetraacetic acid (EGTA).
[0119] The method disclosed herein permits production of a ternary
cathode material having good uniformity. The combination of
excellent cycling performance and high overall capacity makes the
resulting lithium-ion batteries an improved power source,
particularly for high energy applications, such as electric
vehicles.
[0120] The following examples are presented to exemplify
embodiments of the invention. All numerical values are approximate.
When numerical ranges are given, it should be understood that
embodiments outside the stated ranges may still fall within the
scope of the invention. Specific details described in each example
should not be construed as necessary features of the invention.
EXAMPLES
[0121] Particle size distributions of the dried cathode material
precursor and the cathode material were measured by a laser
diffraction particle size distribution analyzer (Mastersizer 3000,
Malvern Instruments Ltd., UK). Samples were delivered to the
measurement area of the optical bench in a stable state of
dispersion. The measurement of particle sizes was carried out while
the particles were sufficiently dispersed.
[0122] The tapped density measurement of the cathode material was
carried out by mechanically tapping a graduated measuring cylinder
(100 mL) containing the sample (mass W). After observing the
initial powder volume, the measuring cylinder was mechanically
tapped by a tapping machine until no further volume (V in cm.sup.3)
change was observed. The TD was calculated as TD=W/V. The TD
measurement was carried out on a tapped density tester (SVM 223,
obtained from Erweka GmbH, Germany).
[0123] The thickness of pouch cells was measured by a micrometer
(293-240-30, Mitutoyo Corporation, Japan) having a measuring range
from 0 mm to 25 mm.
Example 1
A) Preparation of a First Solution
[0124] A first solution was prepared by dissolving 4.38 kg of
nickel sulphate hexahydrate (NiSO.sub.4.6H.sub.2O; #227676,
obtained from Sigma-Aldrich, US), 2.81 kg of manganese sulphate
monohydrate (MnSO.sub.4.H.sub.2O; #31425, obtained from
Sigma-Aldrich, US) and 4.68 kg of cobalt sulphate heptahydrate
(CoSO.sub.4.7H.sub.2O; #C6768, obtained from Sigma-Aldrich, US) in
20 L of de-ionzied water. The total concentration of the metal ions
in the first solution was 2.5 mol/L.
B) Preparation of a Second Solution
[0125] A second solution was prepared by dissolving 5.3 kg of
sodium carbonate (Na.sub.2CO.sub.3; #791768, obtained from
Sigma-Aldrich, US) in 20 L of de-ionized water. The concentration
of the sodium carbonate in the second solution was 2.5 mol/L.
C) Preparation of a Suspension
[0126] The first and second solutions were pre-heated and incubated
in a water bath at 60.degree. C. to obtain a pre-heated first
solution and a pre-heated second solution. A static mixer made of
polypropylene (obtained from Dongguan Yihui Adhesive Co. Ltd.,
China), having a diameter of 5 cm and a length of 50 cm, and
equipped with a heating jacket (obtained from Jiangsu Tianling
Instruments Co. Ltd.) was used. The static mixer was heated to
60.degree. C. The pre-heated first solution and the pre-heated
second solution were fed into a first inlet and a second inlet of
the pre-heated static mixer at a flow rate of 10 L/hour
respectively to form a co-precipitating solution in the static
mixer. The static mixer was coupled to an ultrasonicator (G-100ST;
obtained from Shenzhen Geneng Cleaning Equipment Co. Ltd., China)
which was operated continuously at 500 W. A suspension was eluted
from an outlet of the static mixer. The flow rate measured at the
outlet of the static mixer was 20.2 L/hour. The co-precipitating
solution was mixed in the static mixer for about 40 seconds. The pH
of the co-precipitating solution was continuously monitored and
maintained by an automatic pH controller (obtained from Sichen
Instruments Technology Co. Ltd, China) coupled to the outlet of the
static mixer. The pH controller comprised two peristaltic pumps for
controlling the flow rate of the pre-heated first solution and the
pre-heated second solution to maintain a constant pH in the
co-precipitating solution. The pH of the co-precipitating solution
is shown in Table 1 below.
D) Preparation of a Cathode Material Precursor
[0127] The suspension was filtered and washed with de-ionized water
3 times for 15 minutes each to obtain a cathode material precursor.
The cathode material precursor was dried in an oven (DZF-6050,
obtained from Shanghai Hasuc Instrument Manufacture Co. Ltd.,
China) at 80.degree. C. for 6 hours to obtain a dried cathode
material precursor. The yield of the dried cathode material
precursor is shown in Table 2 below. The particle size distribution
of the dried cathode material precursor is shown in Table 3
below.
E) Preparation of a Cathode Material
[0128] A solid mixture was obtained by mixing the dried cathode
material precursor with 3.774 kg of lithium carbonate
(Li.sub.2CO.sub.3, obtained from Aladdin Industries Corporation,
China) in a molar ratio of lithium salt to total metal salt (Ni,
Mn, Co) of 1.02:1 in a blender (obtained from VWR, US) operated at
a stirring speed of 5,000 rpm for 1 hour. The solid mixture was
then heated in a rotary furnace (KY-R-SJQ130, obtained from
Xianyang Institute of Ceramics Industry, Thermal Equipment Center,
Shanxi, China) rotating with a speed of about 0.5 round per minute
in open air to 460.degree. C. at a heating rate of 2.degree.
C./minute and further calcined for 5 hours at 460.degree. C. Then,
the temperature in the rotary furnace was increased to 900.degree.
C. at a heating rate of 2.degree. C./minute and the mixture was
further calcined for 10 hours. The calcined product was cooled to
room temperature at a rate from 2.degree. C./minute to 5.degree.
C./minute for 6 hours. A cathode material NMC333 was obtained by
sieving the calcined product through a 300 mesh sieve. The
formulation of Example 1 is shown in Table 1 below. The yield,
particle size distribution and tapped density of the cathode
material are shown in Tables 2, 3 and 4 below respectively.
F) Preparation of a Cathode Slurry
[0129] A positive electrode slurry was prepared by mixing 91 wt. %
cathode material prepared in Example 1, 4 wt. % carbon black
(SuperP; Timcal Ltd, Bodio, Switzerland), and 5 wt. %
polyvinylidene fluoride (PVDF; Solef.RTM. 5130, obtained from
Solvay S.A., Belgium) in N-methyl-2-pyrrolidone (NMP; purity of
.gtoreq.99%, Sigma-Aldrich, US) to form a slurry having a solid
content of 50 wt. %. The slurry was homogenized by a planetary
stirring mixer (200 L mixer, Chienemei Industry Co. Ltd., China)
for 6 hours operated at a stirring speed of 20 rpm and a dispersing
speed of 1,500 rpm to obtain a homogenized slurry.
G) Assembling of Coin Cells
[0130] A positive electrode was prepared by coating the cathode
slurry onto one side of an aluminium foil having a thickness of 9
.mu.m using a doctor blade coater (MSK-AFA-III; obtained from
Shenzhen KejingStar Technology Ltd., China) with an area density of
about 7 mg/cm.sup.2. The coated film on the aluminium foil was
dried by an electrically heated conveyor oven set at 90.degree. C.
for 2 hours.
[0131] The electrochemical performance of the cathode prepared
above was tested in CR2032 coin cells assembled in an argon-filled
glove box. The coated cathode sheet was cut into disc-form positive
electrodes for coin cell assembly. A lithium metal foil having a
thickness of 500 .mu.m was used as a counter electrode. The
electrolyte was a solution of LiPF.sub.6 (1 M) in a mixture of
ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl
carbonate (DMC) in a volume ratio of 1:1:1. The electrochemical
performance of the coin cell of Example 1 was measured and is shown
in Table 6 below.
H) Preparation of a Pouch Cell
I) Preparation of a Positive Electrode
[0132] The homogenized cathode slurry prepared above was coated
onto both sides of an aluminium foil having a thickness of 20 .mu.m
using a transfer coater (ZY-TSF6-6518, obtained from Jin Fan Zhanyu
New Energy Technology Co. Ltd., China) with an area density of
about 26 mg/cm.sup.2. The coated films on the aluminium foil were
dried for 3 minutes by a 24-meter-long conveyor hot air drying oven
as a sub-module of the transfer coater operated at a conveyor speed
of about 8 meters/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 55.degree. C. to the outlet temperature of
80.degree. C.
II) Preparation of a Negative Electrode
[0133] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. % PVDF in NMP to
form a slurry having a solid content of 50 wt. %. The slurry was
homogenized by a planetary mixer.
[0134] The slurry was coated onto both sides of a copper foil
having a thickness of 9 .mu.m using a transfer coater with an area
density of about 15 mg/cm.sup.2. The coated films on the copper
foil were dried at about 50.degree. C. for 2.4 minutes by a
24-meter-long conveyor hot air dryer operated at a conveyor speed
of about 10 meters/minute to obtain a negative electrode.
III) Assembling of a Pouch Cell
[0135] After drying, the resulting cathode film and anode film were
used to prepare the cathode and anode respectively by cutting them
into individual electrode plates. A pouch cell was assembled by
stacking the cathode and anode electrode plates alternatively and
then packaged in a case made of an aluminium-plastic laminated
film. The cathode and anode electrode plates were kept apart by
separators and the case was pre-formed. An electrolyte was then
filled into the case holding the packed electrodes in high-purity
argon atmosphere with moisture and oxygen content less than 1 ppm.
The electrolyte was a solution of LiPF.sub.6 (1 M) in a mixture of
ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl
carbonate (DMC) in a volume ratio of 1:1:1. After electrolyte
filling, the pouch cell was vacuum sealed and then mechanically
pressed using a punch tooling with standard square shape. The
electrochemical performance of the pouch cell of Example 1 was
measured and is shown in Table 6 below. The volume expansions of
the pouch cell of Example 1 at the end of the first and twentieth
charging processes were measured and the results are shown in Table
7 below.
Example 2
[0136] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the molar ratio of Ni, Co and
Mn was adjusted to obtain a cathode material NMC532. A first
solution was prepared by dissolving 6.57 kg of nickel sulphate
hexahydrate, 2.53 kg of manganese sulphate monohydrate and 2.81 kg
of cobalt sulphate heptahydrate in de-ionized water. The total
concentration of the metal ions in the first solution was 2.5
mol/L. The formulation of Example 2 is shown in Table 1 below.
Example 3
[0137] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the molar ratio of Ni, Co and
Mn was adjusted to obtain a cathode material NMC622. A first
solution was prepared by dissolving 7.89 kg of nickel sulphate
hexahydrate, 1.69 kg of manganese sulphate monohydrate and 2.81 kg
of cobalt sulphate heptahydrate in de-ionized water. The total
concentration of the metal ions in the first solution was 2.5
mol/L. The formulation of Example 3 is shown in Table 1 below.
Example 4
[0138] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the molar ratio of Ni, Co and
Mn was adjusted to obtain a cathode material NMC811. A first
solution was prepared by dissolving 10.5 kg of nickel sulphate
hexahydrate, 0.845 kg of manganese sulphate monohydrate and 1.41 kg
of cobalt sulphate heptahydrate in de-ionized water. The total
concentration of the metal ions in the first solution was 2.5
mol/L. The formulation of Example 4 is shown in Table 1 below.
[0139] FIG. 2 shows the SEM image of the surface morphology of the
cathode material. The morphology of the cathode material was
characterized by a scanning electron microscope (S4800, Hitachi,
Japan).
Example 5
[0140] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the cathode material NCA was
prepared and a first solution was prepared by dissolving 10.5 kg of
nickel sulphate hexahydrate, 2.11 kg of cobalt sulphate
heptahydrate and 1.14 kg of anhydrous aluminium sulphate in
de-ionized water. The total concentration of the metal ions in the
first solution was 2.5 mol/L. The formulation of Example 5 is shown
in Table 1 below.
Example 6
[0141] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the molar ratio of Li, Ni, Co
and Mn was adjusted to obtain a cathode material
0.4Li.sub.2MnO.sub.3.0.6LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2.
A first solution was prepared by dissolving 2.63 kg of nickel
sulphate hexahydrate, 5.07 kg of manganese sulphate monohydrate and
2.81 kg of cobalt sulphate heptahydrate in de-ionized water. A
solid mixture was obtained by mixing the dried cathode material
precursor with 5.18 kg of lithium carbonate in a molar ratio of
lithium salt to total metal salt of 1.4:1 in a blender operated at
a stirring speed of 5,000 rpm for 1 hour. The formulation of
Example 6 is shown in Table 1 below.
Example 7
[0142] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that sodium hydroxide (NaOH,
obtained from Aladdin Industries Corporation, China) was used
instead of sodium carbonate as a precipitating agent. A second
solution was prepared by dissolving 4 kg of sodium hydroxide in
de-ionized water. The concentration of sodium hydroxide in the
second solution was 5 mol/L. The formulation of Example 7 is shown
in Table 1 below.
Example 8
[0143] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that a static mixer having a
diameter of 10 cm and a length of 80 cm was used and the
co-precipitating solution was mixed in the static mixer for about
60 seconds. The formulation of Example 8 is shown in Table 1
below.
Example 9
[0144] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that the static mixer was operated
for 24 hours. A first solution was prepared by dissolving 252 kg of
nickel sulphate hexahydrate, 20.3 kg of manganese sulphate
monohydrate and 33.8 kg of cobalt sulphate heptahydrate in 240 L of
de-ionized water. A second solution was prepared by dissolving
127.2 kg of sodium carbonate in 240 L of de-ionized water. The flow
rate measured at the outlet of the static mixer was 20 L/hour. The
formulation of Example 9 is shown in Table 1 below. The flow rate
of suspension discharged from the outlet of the static mixer of
Example 9 is shown in Table 5 below.
Comparative Example 1
[0145] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the pH of the co-precipitation
solution was not adjusted. The formulation of Comparative Example 1
is shown in Table 1 below.
Comparative Example 2
[0146] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that the pH of the co-precipitation
solution was not adjusted. The formulation of Comparative Example 2
is shown in Table 1 below.
Comparative Example 3
[0147] A coin cell and a pouch cell were prepared in the same
manner as in Example 5, except that the pH of the co-precipitation
solution was not adjusted. The formulation of Comparative Example 3
is shown in Table 1 below.
Comparative Example 4
[0148] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that the first and second solutions
were not pre-heated. The formulation of Comparative Example 4 is
shown in Table 1 below.
Comparative Example 5
[0149] A coin cell and a pouch cell were prepared in the same
manner as in Example 5, except that the first and second solutions
were not pre-heated. The formulation of Comparative Example 5 is
shown in Table 1 below.
Comparative Example 6
[0150] A coin cell and a pouch cell were prepared in the same
manner as in Example 6, except that the first and second solutions
were not pre-heated. The formulation of Comparative Example 6 is
shown in Table 1 below.
Comparative Example 7
[0151] A coin cell and a pouch cell were prepared in the same
manner as in Example 3, except that a static mixer without a
heating jacket was used. The formulation of Comparative Example 7
is shown in Table 1 below.
Comparative Example 8
[0152] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that Li.sub.2CO.sub.3 and the dried
cathode material precursor were mixed in a molar ratio of 1.07:1.
The formulation of Comparative Example 8 is shown in Table 1
below.
Comparative Example 9
[0153] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that the first and second solutions
were mixed with mechanical stirring instead of a static mixer. A
suspension was prepared by mixing a first solution and a second
solution in a 50 L vessel (obtained from Zhengzhou Ketai Laboratory
Instruments Co. Ltd, China) at a speed of 1,000 rpm for 10 hours.
The first and second solutions were respectively pumped to a 50 L
vessel at a flow rate of 10 L/hour. The formulation of Comparative
Example 9 is shown in Table 1 below.
Comparative Example 10
[0154] A coin cell and a pouch cell were prepared in the same
manner as in Example 3, except that the first and second solutions
were mixed with mechanical stirring instead of a static mixer. A
suspension was prepared by mixing a first solution and a second
solution in a 50 L vessel at a speed of 1,000 rpm for 10 hours. The
first and second solutions were respectively pumped to a 50 L
vessel at a flow rate of 10 L/hour. The formulation of Comparative
Example 10 is shown in Table 1 below.
Comparative Example 11
[0155] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that the first and second solutions
were mixed with mechanical stirring instead of a static mixer. A
suspension was prepared by mixing a first solution and a second
solution in a 50 L vessel at a speed of 1,000 rpm for 10 hours. The
first and second solutions were respectively pumped to a 50 L
vessel at a flow rate of 10 L/hour. The formulation of Comparative
Example 11 is shown in Table 1 below.
Comparative Example 12
[0156] A coin cell and a pouch cell were prepared in the same
manner as in Example 5, except that the first and second solutions
were mixed with mechanical stirring instead of a static mixer. A
suspension was prepared by mixing a first solution and a second
solution in a 50 L vessel at a speed of 1,000 rpm for 24 hours. The
first and second solutions were respectively pumped to a 50 L
vessel at a flow rate of 10 L/hour. The formulation of Comparative
Example 12 is shown in Table 1 below.
Comparative Example 13
[0157] A coin cell and a pouch cell were prepared in the same
manner as in Example 4, except that the ultrasonicator was not used
and the static mixer was operated continuously. The formulation of
Comparative Example 13 is shown in Table 1 below. The flow rate of
the suspension discharged from the outlet of the static mixer of
Comparative Example 13 is shown in Table 5 below.
Comparative Example 14
[0158] A coin cell and a pouch cell were prepared in the same
manner as in Example 1, except that sodium carbonate and ammonia
solution were used instead of sodium carbonate for preparing a
second solution; the pH controller was not used; the first and
second solutions were not pre-heated; and a static mixer without a
heating jacket was used. A second solution was prepared by
dissolving 14 kg of sodium carbonate in 20 L of de-ionized water,
and adding 4.25 L of ammonia solution. The concentration of sodium
carbonate and ammonia in the second solution were 5.44 mol/L and
10.3 mol/L respectively.
[0159] The first and second solutions were fed into a first inlet
and a second inlet of the static mixer at a flow rate of 5 L/minute
respectively to form a co-precipitating solution in the static
mixer. The pH of the co-precipitating solution was not adjusted by
the pH controller. The pH of the co-precipitating solution is shown
in Table 1 below.
[0160] The suspension eluted from the outlet of the static mixer
was left to stand for 2 hours, filtered and washed with de-ionized
water 3 times for 15 minutes each to obtain the cathode material
precursor. The cathode material precursor was dried in a spray
dryer. The yield of the dried cathode material precursor is shown
in Table 2 below. The dried cathode material precursor was calcined
at 460.degree. C. for 5 hours in a rotary furnace rotating with a
speed of about 0.5 round per minute.
[0161] A solid mixture was obtained by mixing the dried cathode
material precursor with lithium salt in a molar ratio of lithium
salt to total metal salt (Ni, Mn, Co) of 1.02:1 in a planetary-type
ball mill (Changsha MITR Instrument & Equipment Co. Ltd.,
China) with zirconium oxide (ZrO.sub.2) balls operated at a
rotation speed of 150 rpm and spinning speed of 250 rpm. After
mixing for 2 hours, a homogenized solid mixture was obtained.
[0162] The solid mixture was then calcined in a rotary furnace
rotating with a speed of about 0.5 round per minute in open air at
900.degree. C. for 10 hours. The calcined product was cooled to
room temperature at a rate from 3.degree. C./minute to 5.degree.
C./minute for 6 hours. The formulation of Comparative Example 14 is
shown in Table 1 below. The yield, particle size distribution and
tapped density of the cathode material are shown in Table 2, 3 and
4 below respectively.
Comparative Example 15
[0163] A coin cell and a pouch cell were prepared in the same
manner as in Example 14, except that NMC811 was used instead of
NMC333 as a cathode material. The formulation of Comparative
Example 15 is shown in Table 1 below.
TABLE-US-00001 TABLE 1 Temp. control of Temp. of heating jacket CoP
Ni:Mn:Co:Al Precipitating pH of CoP and 1.sup.st and 2.sup.nd
solution ratio agent solution solutions (.degree. C.) Mixing
Example 1 1:1:1:0 Na.sub.2CO.sub.3 10.0 .+-. 0.1 Yes 60 Static
mixer Example 2 5:3:2:0 Na.sub.2CO.sub.3 10.5 .+-. 0.1 Yes 60
Static mixer Example 3 6:2:2:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1 Yes
60 Static mixer Example 4 8:1:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1
Yes 60 Static mixer Example 5 8:0:1.5:0.5 Na.sub.2CO.sub.3 11.0
.+-. 0.1 Yes 60 Static mixer Example 6 1:3:1:0 Na.sub.2CO.sub.3
11.0 .+-. 0.1 Yes 60 Static mixer Example 7 8:1:1:0 NaOH 11.0 .+-.
0.1 Yes 60 Static mixer .sup.1 Example 8 8:1:1:0 Na.sub.2CO.sub.3
11.0 .+-. 0.1 Yes 60 Static mixer Example 9 8:1:1:0
Na.sub.2CO.sub.3 11.0 .+-. 0.1 Yes 60 Static mixer (run 24 hrs)
Comparative 1:1:1:0 Na.sub.2CO.sub.3 9.0-11.0 Yes 60 Static mixer
Example 1 (un-adjusted) Comparative 8:1:1:0 Na.sub.2CO.sub.3
9.0-12.0 Yes 60 Static mixer Example 2 (un-adjusted) Comparative
8:0:1.5:0.5 Na.sub.2CO.sub.3 9.0-11.0 Yes 60 Static mixer Example 3
(un-adjusted) Comparative 8:1:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1
1.sup.st and 2.sup.nd 25-45 Static mixer Example 4 solutions (not
preheated) Comparative 8:0:1.5:0.5 Na.sub.2CO.sub.3 11.0 .+-. 0.1
1.sup.st and 2.sup.nd 25-40 Static mixer Example 5 solutions (not
preheated) Comparative 1:3:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1
1.sup.st and 2.sup.nd 25-45 Static mixer Example 6 solutions (not
preheated) Comparative 6:2:2:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1
Static mixer 40-60 Static mixer Example 7 without heating jacket
.sup.2 Comparative 8:1:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1 Yes 60
Static mixer Example 8 Comparative 1:1:1:0 Na.sub.2CO.sub.3 10.0
.+-. 0.2 Yes 60 Mechanical Example 9 stirring Comparative 6:2:2:0
Na.sub.2CO.sub.3 11.0 .+-. 0.2 Yes 60 Mechanical Example 10
stirring Comparative 8:1:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.2 Yes 60
Mechanical Example 11 stirring Comparative 8:0:1.5:0.5
Na.sub.2CO.sub.3 11.0 .+-. 0.2 Yes 60 Mechanical Example 12
stirring Comparative 8:1:1:0 Na.sub.2CO.sub.3 11.0 .+-. 0.1 Yes 60
Static mixer Example 13 (0-4 hrs); without 11.0 .+-. 1 ultrasonica-
(5-10 hrs) tion Comparative 1:1:1:0 Na.sub.2CO.sub.3 9.5-10.5
Static mixer 20 Static mixer Example 14 without heating jacket
Comparative 8:1:1:0 Na.sub.2CO.sub.3 10.5-11.5 Static mixer 20
Static mixer Example 15 without heating jacket Note: .sup.1 A
static mixer having a diameter of 10 cm and a length of 80 cm was
used. .sup.2 Li.sub.2CO.sub.3 and the dried cathode material
precursor were mixed in a molar ratio of 1.07:1.
[0164] Table 2 shows the yield of the dried cathode material
precursors and the cathode materials of Examples 1-9 and
Comparative Examples 1-15 respectively.
TABLE-US-00002 TABLE 2 Dried cathode material precursor Cathode
material yield (%) yield (%) Example 1 94.5 93.5 Example 2 94.1
94.3 Example 3 93.4 94.4 Example 4 93.5 92.7 Example 5 94.4 93.4
Example 6 96.1 95.1 Example 7 96.1 95.2 Example 8 96.3 95.6 Example
9 95.7 94.9 Comparative Example 1 83.6 82.4 Comparative Example 2
81.5 82.4 Comparative Example 3 82.4 85.2 Comparative Example 4
82.4 83.1 Comparative Example 5 81.0 83.7 Comparative Example 6
80.3 84.1 Comparative Example 7 82.3 83.5 Comparative Example 8
81.2 81.5 Comparative Example 9 76.8 78.5 Comparative Example 10
80.4 80.5 Comparative Example 11 81.3 80.4 Comparative Example 12
80.9 79.5 Comparative Example 13 75.1 74.3 Comparative Example 14
80.5 79.5 Comparative Example 15 80.2 79.3
[0165] Table 3 shows the D50 value and the D90/D10 ratio of the
dried cathode material precursors and cathode materials of Examples
1-9 and Comparative Examples 1-15 respectively. The dried cathode
material precursors and cathode materials of Examples 1-9 have
smaller particle sizes than the dried cathode material precursors
and cathode materials of Comparative Examples 1-15. In addition,
the dried cathode material precursors and cathode materials of
Examples 1-9 show more uniform particle size distributions.
TABLE-US-00003 TABLE 3 D50 of dried D90/D10 of dried cathode
material cathode material D50 of cathode D90/D10 of precursor
(.mu.m) precursor material (.mu.m) cathode material Example 1 5.6
1.5 8.5 1.6 Example 2 4.7 1.6 8.9 1.4 Example 3 5.1 1.6 8.3 1.5
Example 4 3.8 1.8 7.5 1.7 Example 5 4.3 1.4 7.6 1.5 Example 6 5.8
1.6 8.7 1.8 Example 7 3.5 1.5 8.5 1.6 Example 8 5.1 1.7 8.1 1.7
Example 9 5.4 1.6 7.9 1.6 Comparative Example 1 13.7 2.8 16.9 2.6
Comparative Example 2 13.5 2.7 17.5 2.6 Comparative Example 3 14.6
2.8 18.1 2.7 Comparative Example 4 14.1 2.9 17.4 2.8 Comparative
Example 5 16.9 2.9 19.1 2.9 Comparative Example 6 14.8 2.6 17.8 2.4
Comparative Example 7 14.7 2.8 17.5 2.7 Comparative Example 8 13.5
2.9 17.1 2.5 Comparative Example 9 18.9 3.0 19.6 2.9 Comparative
Example 10 17.1 2.7 18.2 2.6 Comparative Example 11 17.2 2.8 18.5
2.7 Comparative Example 12 17.1 2.9 18.2 2.9 Comparative Example 13
19.5 3.1 20.3 3.5 Comparative Example 14 17.1 2.7 18.1 2.8
Comparative Example 15 17.6 2.8 18.3 2.9
[0166] Table 4 shows the tapped density of the cathode materials of
Examples 1-9 and Comparative Examples 1-15. The cathode materials
of Examples 1-9 have higher tapped densities than the cathode
materials of Comparative Examples 1-15. The higher tapped densities
allow one to obtain battery having higher capacity.
TABLE-US-00004 TABLE 4 Tapped density of cathode material
(g/cm.sup.3) Example 1 2.6 Example 2 2.6 Example 3 2.7 Example 4
2.8 Example 5 2.8 Example 6 2.6 Example 7 2.6 Example 8 2.8 Example
9 2.8 Comparative Example 1 2.3 Comparative Example 2 2.1
Comparative Example 3 2.2 Comparative Example 4 2.3 Comparative
Example 5 2.1 Comparative Example 6 2.1 Comparative Example 7 2.1
Comparative Example 8 2.2 Comparative Example 9 1.9 Comparative
Example 10 2.0 Comparative Example 11 2.0 Comparative Example 12
2.1 Comparative Example 13 2.0 Comparative Example 14 2.1
Comparative Example 15 2.0
[0167] Table 5 shows the flow rate of the suspension discharged
from the outlet of the static mixer of Example 9 and Comparative
Example 13 over a time period of 24 hours. The flow rate of the
suspension discharged from the outlet of the static mixer of
Example 9 was almost constant during operation. It was observed
that the flow rate of the suspension discharged from the outlet of
the static mixer of Comparative Example 13 decreased with time and
stopped at the eleventh hour.
TABLE-US-00005 TABLE 5 Flow rate (L/hour) Time Comparative Time
Flow rate (L/hour) (hour) Example 9 Example 13 (hour) Example 9 0
20.1 20.2 13 19.8 1 19.6 20.0 14 19.8 2 19.8 19.5 15 19.9 3 20.3
18.4 16 20.2 4 20.2 17.5 17 20.2 5 19.7 15.1 18 19.7 6 19.9 12.5 19
20.0 7 19.9 8.5 20 20.1 8 20.4 4.8 21 19.7 9 20.0 1.2 22 19.8 10
19.9 0.1 23 19.8 11 20.1 0 24 20.0 12 19.6 / / /
[0168] The cyclability performance of the coin cells of Examples
1-9 and Comparative example 1-15 was tested by charging and
discharging at a constant current rate of 1C between 3.0 V and 4.3
V. The cyclability performance of the pouch cells of Example 1-9
and Comparative example 1-15 was tested by charging and discharging
at a constant current rate of 1C between 3.0 V and 4.2 V. Test
results of cyclability performance of the coin cells and pouch
cells are shown in Table 6 below.
TABLE-US-00006 TABLE 6 Capacity retention Capacity retention of
Cycle life of pouch Specific capacity of coin cell after coin cell
after cell with 80% (mAh/g) 50 cycles (%) 100 cycles (%) capacity
retention Example 1 145.5 99.3 98.6 1,085 Example 2 156.2 99.2 98.2
1,060 Example 3 168.3 99.0 98.1 1,030 Example 4 182.4 98.6 98.0
1,040 Example 5 178.2 99.0 98.2 1,040 Example 6 225.7 98.1 98.0 850
Example 7 183.2 98.3 98.2 1,050 Example 8 184.2 98.4 98.1 1,060
Example 9 183.2 98.4 98.2 1,030 Comparative 138.4 85.7 70.2 740
Example 1 Comparative 168.3 84.3 72.5 840 Example 2 Comparative
168.9 83.6 72.5 860 Example 3 Comparative 165.7 84.7 71.5 820
Example 4 Comparative 174.8 83.5 73.7 680 Example 5 Comparative
200.8 83.7 71.5 420 Example 6 Comparative 162.8 86.2 70.3 680
Example 7 Comparative 180.5 83.7 75.2 560 Example 8 Comparative
133.6 85.2 72.5 760 Example 9 Comparative 150.3 83.7 70.5 780
Example 10 Comparative 170.3 82.1 70.3 760 Example 11 Comparative
171.4 82.5 72.4 680 Example 12 Comparative 161.7 84.0 74.5 660
Example 13 Comparative 120.3 82.0 70.8 760 Example 14 Comparative
130.4 83.1 71.2 750 Example 15
[0169] The coin cells and pouch cells of Examples 1-9 showed
excellent cyclability. Battery cells prepared by the method
disclosed herein show better cyclability than the ones prepared by
conventional methods, especially in the case of the NMC622 and
NMC811 cathode materials.
[0170] The pouch cells of Examples 1-9 and Comparative Examples
1-15 were fully charged with a 0.1 C rate. The volume expansions of
the cells at the end of the first and twentieth charging processes
at 0.1C were measured. The results are shown in Table 7 below.
TABLE-US-00007 TABLE 7 Thickness of pouch cell (mm) Volume
expansion (%) After 1.sup.st After 20.sup.th After 1.sup.st After
20.sup.th Example Initial discharge discharge discharge discharge
Example 1 3.58 3.73 3.73 4.1 4.2 Example 2 3.59 3.74 3.75 4.3 4.4
Example 3 3.57 3.74 3.74 4.9 4.9 Example 4 3.60 3.87 3.79 5.1 5.2
Example 5 3.58 3.77 3.77 5.2 5.2 Example 6 3.59 3.78 3.78 5.3 5.4
Example 7 3.58 3.77 3.77 5.2 5.3 Example 8 3.58 3.76 3.76 5.1 5.1
Example 9 3.59 3.78 3.78 5.2 5.3 Comparative 3.58 3.82 3.83 6.8 6.9
Example 1 Comparative 3.58 3.86 3.86 7.8 7.8 Example 2 Comparative
3.58 3.84 3.84 7.2 7.3 Example 3 Comparative 3.59 3.87 3.87 7.9 7.9
Example 4 Comparative 3.58 3.84 3.84 7.3 7.4 Example 5 Comparative
3.58 3.86 3.86 7.9 7.9 Example 6 Comparative 3.57 3.83 3.83 7.3 7.3
Example 7 Comparative 3.59 3.89 3.89 8.5 8.5 Example 8 Comparative
3.59 3.82 3.82 6.3 6.4 Example 9 Comparative 3.58 3.84 3.84 7.2 7.3
Example 10 Comparative 3.58 3.86 3.86 7.9 7.9 Example 11
Comparative 3.59 3.86 3.86 7.4 7.5 Example 12 Comparative 3.58 3.86
3.86 7.9 7.9 Example 13 Comparative 3.58 3.84 3.84 7.2 7.3 Example
14 Comparative 3.59 3.86 3.86 7.4 7.5 Example 15
[0171] The experimentally measured volume expansions of the cells
of Examples 1-9 were much smaller than the values of Comparative
Examples 1-15. The volume expansion of the cell of Comparative
Example 8 is higher than that of Example 4 because of higher
lithium content in the cathode material of Comparative Example 8.
The results also show that the cells of Example 1-9 have improved
safety performance over the cells of Comparative Example 1-15.
[0172] While the invention has been described with respect to a
limited number of embodiments, the specific features of one
embodiment should not be attributed to other embodiments of the
invention. In some embodiments, the methods may include numerous
steps not mentioned herein. In other embodiments, the methods do
not include, or are substantially free of, any steps not enumerated
herein. Variations and modifications from the described embodiments
exist. The appended claims intend to cover all those modifications
and variations as falling within the scope of the invention.
* * * * *